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Friday, April 19, 2013

Drombler Commons: JavaFX controls for the new Date & Time API (JSR-310)

I managed to open source and release two more libraries I mainly worked on in spring 2012. They form the first 2 components of this first Early Access version of Drombler Commons: Drombler Commons - FX - Core and Drombler Commons - FX - Date and Time.

The library is available from Maven Central (along with the sources and javadoc artifact):

The library contains the necessary OSGi meta data and thus is ready for use in a Drombler FX application, but it should also be useable outside an OSGi framework.

Drombler Commons - FX - Date and Time

This component is an extension of Drombler Commons - FX - Core and provides controls and DataRenderers for the new Date and Time API (JSR-310), which is planned to be added to the upcoming Java SE 8 release.

This library provides the following custom controls:

MonthOfYearComboBox: a ComboBox to choose an instance of the MonthOfYear enum.The text representations of MonthOfYear are locale sensitive (as provided by the Date and Time API).

YearMonthSpinner: a skinnable Spinner control for YearMonth. The default Skin provides optional Buttons to spin through YearMonth instances and provides a MonthOfYearComboBox and a YearField to let the user change the MonthOfYear and Year directly. The text representations of MonthOfYear are locale sensitive (as provided by the Date and Time API).

LocalDateFixedYearMonthChooser: a skinnable Control which allows the user to select a LocalDate in a given YearMonth.As the complicated name hints, this control is intended as a building block for other controls rather than to be used in applications directly.

LocalDateChooser: a skinnable Control which allows the user to select a LocalDate.The default Skin combines a LocalDateFixedYearMonthChooser with a YearMonthSpinner.

The first sample of this control uses the following configuration:

selectedDate.max: now.plusWeeks(3) (now=3rd April 2013)

selectedDate.min: now.minusMonths(19) (now=3rd April 2013)

previousMonths: 1

nextMonths: 1

locale: en_US (English, United States)

This sample shows three months at a time: the current year month + 1 previous month + 1 next month.
Note that the previous year and the previous month scroll buttons are only shown for the first chooser and the next year and the next month scroll buttons are only shown for the last chooser. The other scroll buttons are hidden.

Since the selectedDate property is a limited property, you can specify an optional min and max date.
Note that the MonthOfYearComboBox limits the possible values depending on the values set for the min and max date. (Here: the max YearMonth of the center chooser is April 2013, so the possible values for MonthOfYear in 2013 for the previous chooser are: January - March).
Also note that the year and the month scroll buttons get enabled and disabled depending on the values set for the min and max date. (Here: the year scroll button on the right hand side is disabled.).
The day buttons are also disabled if the dates are out of range (here: the day buttons are disabled from 25th April 2013 onwards).

As some months span up to 6 weeks, at least 6 weeks are always shown, where
the first week is the week with the first day of the month.

The week of the year is shown on the left-hand side.

The dates are colored differently depending on if they are in the shown month or not.

Here is another sample of the same control with the following configuration:

previousWeeks: 2

nextWeeks: 1

showingWeekOfYear: false

showingYearScrollButton: false

locale: de_CH (German, Switzerland)

This sample only shows a single month at a time.

The
previousWeeks and the nextWeeks are added to the standard 6 weeks, so this sample shows 9 weeks.

Note
that in this sample, the week of year column at the left-hand side of
the control and the year scroll buttons of the YearMonthSpinner are
hidden.

Also note that not only the days of the week and the months are now shown in German, but the week starts now with Monday, where when using the en_US locale the week starts with Sunday.
All this locale-sensitive information is provided by the Date and Time API.

LocalDatePicker: a skinnable Control which provides a text field and allows to pick the LocalDate from a control.The default Skin uses a LocalDateChooser in a pop-up window. You can specify a DataRenderer to format the LocalDate in the text field. Note that the text provided by the default DataRenderer is locale sensitive (as provided by the Date and Time API).

The library is available from Maven Central (along with the sources and javadoc artifact):

The library contains the necessary OSGi meta data and thus is ready for use in a Drombler FX application, but it should also be useable outside an OSGi framework.

In order to use the Date and Time API jars inside an OSGi framework, you need to register the system packages. In a Drombler FX application you can add the following configuration to your drombler-fx-application module:

src/main/resources/config.properties

Since the Date and Time API jars replace some core classes, you need to specify the jars on the bootclasspath. On the command line you can add the following java command line argument:

where <JAVAX_TIME_0_6_3_HOME> is the parent directory of the Date and Time API jars.

If this path is stored in an environment variable you can use ${env.JAVAX_TIME_0_6_3_HOME} when you're using the Exec Maven Plugin to run your application.

Project

Possible Next Steps

Visual enhancements: the controls could use some more styling

API enhancements: the API needs to be evaluated. Is the existing API fine? Should something be added? It's also not clear to me right now what parts should be configurable via API only, what parts via CSS only and what parts via API and CSS.

Migrate to Java SE 8: the latest released JARs and Javadoc of the Date and Time API are quite old. But since spring 2012, when I wrote most of this Drombler Commons code, most if not all code of the Date and Time API has been integrated into Java SE 8. So the Drombler Commons code should be migrated to Java SE 8 as well.

Earlier this year a new JavaFX issue has been filed requesting to add a DatePicker control based on the new Date and Time API and people started to work on this issue already.I will check the scope of this issue and if some Drombler Commons code can contribute to solve this issue.

When a core API such as the Date and Time API gets "replaced", you must make sure it integrates well with the existing libraries and frameworks.

The Drombler Commons - FX - Date and Time component provides this integrations for JavaFX and shows that, at least with some additional utility methods, the new Date and Time API is fit for that job.

But I would like to read more about how to integrate the new Date and Time API with other frameworks as well, such as:

Controls for Web GUI toolkits such as JSF

JAXB: There is a guide how to replace XMLGregorianCalendar with java.util.Calendar or java.util.Date and there are the DatatypeConverter and the DatatypeFactory classes which help to convert to and from XML data types.But I haven't found a guide or helper classes to convert to and from the new Date and Time API, yet, though. Especially one which doesn't involve the now legacy API java.util.Calendar and java.util.Date.

JPA: JPA provides support for java.util.Calendar and java.util.Date using the Temporal annotation and the TemporalType enum. The next JPA specification after the Java SE 8 release should add support for as many classes of the Date and Time API as possible, so that these classes can be used in JPA entities as well (the JPA specification is currently part of the Java EE specification and not part of Java SE).